The present invention relates generally to a screen-printing machine, and more particularly to a screen-printing machine having one or more printing stations each of which has at least one movable printing screen and at least one cooperating movable squeegee.
In particular the present invention relates to a screen-printing machine for printing of objects which are being rotated as they travel through the printing machine.
In many instances it is desired to provide an object with a plurality of items of print (e.g. pictures, logos, text or the like) in a single operation, that is in a single pass through the screen printing machine. Each image is to be applied by a different one of the printing stations. Often these objects are in form of cans, bottles or similar elements which are required to be provided with the respective printed images on different portions of their circumference, and which must therefore be rotated during their pass through the printing machine. For this purpose it is known to provide a drive, including a rack which extends past one or more of the printing stations, serving to effect the desired rotation of the object to be printed. If the rack extends past two or more of the printing stations of the printing machine, then it is not necessary to properly orient the object with reference to the printing screen at each successive printing station, since the relative angular position of the object to the respective printing screen is fixed as soon as the object is engaged by its engaging device and the gear, which is connected with the engaging device, meshes with the aforementioned stationary rack.
The concept behind these prior art proposals is advantageous, but the prior art screen-printing machines of this type do have certain disadvantages. Among these is the fact that whenever the diameter of the object to be printed changes, that is if a series of smaller-diameter cans is followed by a series of larger-diameter cans, to name an example, the diameter of the gear which meshes with the fixed rack must be correspondingly changed; in other words, the gear must be replaced with one having a different diameter. This is evidently disadvantageous. Furthermore, the stroke of the squeegee must also be adjusted to the diameter of the different objects to be printed, whenever a change occurs in this diameter. If the screen-printing machines are of the type having two or more printing stations, then the spacing between the individual printing stations must be changed in dependence upon the differential diameters of the objects when a change in the diameters occurs.